Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$190.65	11.367%	$212.3212	$212.32	$212.30	$212.30
Purchase #2	$166.63	8.228%	$180.3403	$180.34	$180.35	$180.30
Purchase #3	$187.57	8.852%	$204.1737	$204.17	$204.15	$204.20
Purchase #4	$223.28	12.141%	$250.3884	$250.39	$250.40	$250.40
Purchase #5	$18.36	13.510%	$20.8404	$20.84	$20.85	$20.80
Purchase #6	$162.40	10.441%	$179.3562	$179.36	$179.35	$179.40
Purchase #7	$100.75	4.313%	$105.0953	$105.10	$105.10	$105.10
7 purchase totals =	$1,049.64		$1,152.5155	$1,152.52	$1,152.50	$1,152.50